In conventional, in the case of applying a bending process to a part of a workpiece by a punch press, a workpiece is moved and positioned in X and Y directions with respect to a processing position, and a slit is processed along an outer shape of a raw material forming the formed product. Further, a slit process is applied also to a periphery of a portion to be bent in a raw material forming the formed product, and a portion surrounded by the slit process is thereafter bent upward, whereby the forming process is executed by raising the portion surrounded by the slit process. As a prior example, there exists a prior art disclosed in Japanese Patent No. 2545176. The prior art is structured such as to bend a bending piece upward by moving up a die chip provided in a lower mold in a state in which the workpiece is fixed by the upper and lower metal molds.
However, when applying a nibbling process of executing the slit process, and a punching operation to an appropriate position of a raw material forming the formed product, a burr is generated in a lower surface of the workpiece. Further, since a surface in a side surrounded and raised by the slit process, that is, an upper surface side of the workpiece forms an inner portion side of the formed product, and a lower surface side of the workpiece in which the burr is generated forms an outer portion side of the formed product, there is a problem that deburring is required.
The present invention is made for the purpose of solving the problem mentioned above, and an object of the present invention is to provide a processing method which can omit deburring by setting a burr generating direction to the same direction (back surface) as a bending direction of a bending piece, and a metal mold used for the processing method.